摘要
本文对西宁黄土剖面古土壤层S_1的721块定向样品进行了详细的岩石磁学和古地磁学研究,获得了Blake亚时转换过程中地球磁场变化特征较精确的记录。主要结果为:1.Blake亚时位于S_1的中下部;与地球磁场方向和强度变化相联系的持续时间分别为3900a和5000a。2.Blake亚时转换过程中地球磁场主体变化特征是由6次快速倒转构成,每次快速倒转所经历的时间为百年的量级,虚地磁极(VGP)极移曲线沿美洲大陆移动,这意味着在此期间地球磁场可能仍以偶极子场为主。3.Blake亚时是一次不成功的极性转换。4.黄土高原西部黄土-古土壤序列的主要磁性矿物可能仍是磁铁矿,次生剩磁主要是粘滞剩磁,当加热温度达到300℃之后即可获得单一组分的特征剩磁。
The records of the Blake polarity subchron have been obtained from soil unit S1 in Xining section of the Chinese Loess Plateau.Paleomagnetism and rock magnetism have been studied by measuring 721 oriented specimens.The main results are as follows: 1.The Blake polarity subchron is located in the middle-low part of S1,and the time duration of this polarity subchron defined by direction and intensity changes of the Earth's magnetic field are about 3900 and 5000 years respectively.2.The main structure of the Earth's magnetic field is consist of 6 rapidly polarity changes,the time occupied by each rapid polarity change is several hundred of years.The Virtual Geomagnetic Pole (VGP) path,confined to a band of longitude over the America,is similar to the paths of this polarity subchron obtained from marine cores in the Mediterranean and lacustrine sediments in the Western USA,suggesting that a dipolar component may be present in the transition field during the Blake subchron.3.The Blake polarity subchron may be defined a 'A borted Polarity Transition'.4.Magnetic mineral in the loess-soil sequences in the Western Loess Plateau may be magnetite,characteristic remanence can be obtained when the specimen is heated above 300℃.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
1993年第5期589-599,共11页
Chinese Journal of Geophysics
基金
国家自然科学基金
关键词
Blake亚时
形态学
黄土
地磁学
Blake polarity subchrou
Morphology
Aborted polarity transition
Xining section
